Determine if phone has been rebooted

Question

I'm trying to detect if an Android device has rebooted since the last time a preference value is set. Ideally, I'd like to do it without the android.permission.RECEIVE_BOOT_COMPLETED permission.

One way I'm thinking about doing this is storing another preference value that contains some sort of session ID. When I update the preference value in question, I'd update the session value as well. When I check the value in the preference for the session value, if it equals the current session value then there has not been a reboot. If the current session value is different than what's saved, then there's been a reboot. Unfortunately, I've been digging through the docs for quite some time now trying to find a session value, and I can't find anything.

I'd like help with one of two things. If you can provide where I could find a value of something similar to a session ID or a boot ID, then I'll use my algorithm. Alternatively, I'd be open to another algorithm to solve the problem. Thank you so much!

Answer 1

This is mad old, but I think I have a good solution that doesn't require any services to run or any special background process.

Simply save the times to persistent memory such as shared preferences. This can be performed at any reference time you need. For me, it's when starting a chronometer so that it can persist even after a reboot. Chronometers relate only to SystemClock.elapsedRealtime(), which is the time since last boot, so you can't use System.currentTimeMillis(), which is the total time since the Unix Epoch (00:00:00 UTC on 1 January 1970).

If you wanted to check if the phone was rebooted only at application start, then add this to your onCreate.

    //Create a SharedPreferences
    SharedPreferences savedKeys = getApplicationContext().getSharedPreferences("MyPref", 0);
    SharedPreferences.Editor editor = savedKeys.edit();
    
    if (((System.currentTimeMillis() - SystemClock.elapsedRealtime())-(savedKeys.getLong("key_oldDelta", 0)))>100) {
    
    //Run code here or set a boolean to true for system reboot.
    
    }
    
    //Save the new values.
    
    editor.putLong("key_oldDelta", (System.currentTimeMillis() - SystemClock.elapsedRealtime()));
    editor.commit();

The following part of the code will get the delta (difference) of the current Unix time and system time since last boot: (System.currentTimeMillis() - SystemClock.elapsedRealtime())

If the system rebooted, those numbers will be larger and smaller respectively compared to what they were before rebooting.

Example: you save times at system time = 100 and Unix time = 1000. You reboot after 450 and restart the app after another 50. 500 has now passed since you recorded the values. They are now 10 and 1500.

New delta: 1500-10=1490

Old delta: 1000-100=900

Delta of deltas: 1490-900=590

The last number will always be higher after a reboot. It doesn't matter how long it's been since the reboot. The difference can only get higher because one number (Unix time) is constantly moving forward and the other is constantly being reset to zero at reboot. My example uses very small numbers to make it easy to understand, but remember the real numbers are in milliseconds, and a fair amount of those have passed since 1970. That's why my code says <100 at the end of the if statement. That gives the app 100 milliseconds to run the math. In reality, it takes more like 1 millisecond, but there's no way a phone will reboot in less than 100, so it's a safe value.

Answer 2

Yes you can do that using Application class and the Non-Static broadcast Receiver ACTION_SHUTDOWN. The Application class got started in two cases

1. Android Device Boot
2. Your Application Starts after it was "Force-Close" it.

When ACTION_SHUTDOWN received use your application Shared-preferences or database to save a boolean shutdown = true when application class starts check this boolean. If it is true then the device is booting , else the user forced your app to stop.

To get more info you can read the following post that I wrote and try the code example in which, I added

1. Application Class
2. Boot Broadcast Receiver (To Show the difference and that both starts)
3. Shutdown broadcast receiver that is register in the Application calss